Thermostatic control



Patented Apr. 5, 1938 UNITED STATES PATENT OFFICE 2,113,227 THERMOSTATIC coN'mo-L John S. Bokeeno, Philadelphia, Pa. Application July 22, 1935, Serial No. 32,488

(01. 2oo 1ss) Claims.

My invention relates to thermostatic controls. More particularly it relates to a thermostatic control which is positive acting and snaps from one position to the other.

One of the objects of my invention is to produce a simple, inexpensive and sensitive thermostatic control. Another object is to devise a control which has a snap action which is fast and positive in performance. A further object is a control unit employing a spring which has a toggle action. Other objects will appear in the detailed specification of my invention.

Figure I is aplan view of one form of my invention,

ll Figure II isan elevational view of the arrangement of Figure I,

Figures III, IV, and V illustrate one form of toggle action,

Figures VI and VII illustrate a simple and preso ferred form of toggle action, and

Figures VIII and IX illustrate a modified toggle action which may be employed.

In Figures I and II, on an insulated base I isfixedly mounted a stud 2. A helical spring 3 of bimetal is secured, by solder or the like, to the stud 2. On the free end 4 of the bimetal strip two arms 5 and 6 are mounted to form a yoke. On the end of arm 5 is threaded an adjustment screw 1. The screw may be locked by a lock nut, not

shown, or a. split end which places a tension on the screw. In the end of screw 1 is mounted a small insulated piece 8 of glass, fibre, or the like.

, On the arm 6 is similarly mounted a screw -9 which has a contact member ll of silver or like metal fastened at its end.

An adjustable arm II is pivotally mounted on base I by a rivet l2. The upright supports l3 and I! are supported by arm II. The supports may be upset from the arm II as shown. The

free end l5 of the arm ll may be bent as shown to form asultable handle and pointer. Between the supports l3 and II and located within a V, or like bearing surface which ofi'ers little friction, is a spring member Hi. This spring member is 4.5 made of phosphor bronze or any metal which possesses a high degree of elasticity and is a good electrical conductor. A contact element I! may be fastened to the spring I6 to engage contact II. In the case of thermostatic controls handling small currents the contacts III- and Il may be omitted.

In Figure I it will be seen that the spring I6 is given a small reverse curve. The curve shown is not a set in the spring material but is the form the spring is made to take by having a length thrust of either I or 9.

greater than the distance between V bearings in the supports l3 and I4 and holding it by the No particular curve is needed. The curve is that which the spring will normally take under the conditions described.

The method of operation depends upon a toggle action of the spring. This may be understood by referring to Figures III to V. Figure III illustrates a spring 20 which bears on the fixedly spaced supports 2| and 22. The spring 20 has a length greater than the fixed distance between the V bearings in 2| and 22. The spring assumes a natural arcuate position as shown in Figure III. If a member such as 23, is thrust against the center of 20, it will gradually assume a position as shown in Figure IV. If the thrust of 23 is continued in the direction shown, the spring 20 will suddenly change its position. It will snap away from 23 and will contact an element 24 as shown in Figure V. In a like manner, the pressure may be applied at 24 to return the spring to the position illustrated in Figure III.

Although the arrangement of Figures III to V may be employed. I prefer the device shown in Figures VI to VII. In. Figure VI 9. spring member 30 is pivoted in the V bearings of the supports 3| and 32. The spring is longer than the distance between the bearings. The added length is taken up by bowing the spring into an S shape curve. It should be understood that the spring is not permanently" set in this position but is flexed as shown. This is an unstable position. The spring is held in this position by the stop 33. If it were not for the stop 33, the spring 30 would assume the position illustrated in Figure V. If a pressure is exerted by 33 in the direction of the arrow the spring will attempt to quickly assume the position illustrated in Figure 111 but will be prevented by the stop 34. The spring will now snap into the position represented by Figure VII. It should be understood that the-springs may be insulated from the contact stops as required to make the proper electrical connections. The spring toggle action which I have just described is the preferred form as shown in Figures I and II. The complete device operates in the following manner: The bimetal element 3 may be made of brass and nickel-steel (36% Ni) or brass and zinc. The diflerence in the coeflicient of expansion of the two metals per degree change in temperature causes the free end 4 to move in a counter or counter clockwise direction as the temperature changes. If 4 moves in a clockwise direction 8 will move l6 until the toggle action snaps l6 into engagement with 3, or 55 ii and it if contact elements are used. As the temperature changes in the reverse direction l will move counterclockwise snapping iii into its original position shown in Figure I.

The pivotal mounting of it permits 55 to be moved to raise or lower the temperature which causes the toggle action to take place. The separation of the contacts or stops i and 9 determines the variation in degrees between the successive toggle positions. It is understood that any electrical circuit may be controlled by suitable connections to 2 and M. Instead of thermostatic control my device may be employed as a hydrostatic control by substituting a suitable hydrostatic responsive element or humidity responsive member in place of In Figures VIII and IX is illustrated another form of spring action. In this connection the spring 56 is securely fastened to support/5i The spring is slidably mounted at 52 and engages a yieldable spring 53. The yieldable spring 53 permits the spring 5% to assume either position shown in Figure VIII or Figure IX as pressures are exerted by 5 or 55. This arrangement is more sensitive than that of Figure III but Figure VI shows the preferred form. In that form sensitivities of less than 1 Fahrenheit may be at-- tained.

The disclosure I have made illustrates one form of a sensitive thermostatic humidity responsive, or pressure control device. Its quick acting toggle contacts prevent feathering or fluttering at the The firm engagement and sharp break prevents pitting and arcing of the contacts. This type of control decreases radio interference. Relay devices may be eliminated by my invention as the quick positive contact action will handle substantial amounts of current.

The arrangements I have shown are the preferable embodiment of my invention but I do not intend to limit it to these exact arrangements as other means within the scope of my invention will be obvious to those skilled in the art.

I claim:

1. In a device of the character described, a temperature responsive member; a pair of elements actuated by said member; a spring contact member characterized by a reverse curve shape,

contacts.

continuously retained in said reverse curve shape. by one or the other of said pair of elements and aiiaaav actuated by said elements to snap the spring contact member into engagement with one or the other of said pair of elements; and means for adlusting the upper or lower limit of response of said temperature responsive member. I

2. In a device of the character described, a temperature responsive member; a pair of ele ments actuated by said member; a spring contact rnember characterised by a reverse curve shape, ,continuously retained in said reverse curve shape by one or the other of said pair of elements and actuated by said elements to snap the spring contact member into engagement with one or the other of said pair of elements; means for adjusting the upper or lower limit of said temperature responsive member, and means for adjusting the 'limits of response of said temperature responsive member.

3. In a device of the character described a responsive member; a pair of elements actuated by said member; an S shape spring member, retained in said 8 shape by engagement with one or the other of said pair of elements, and actuated by one of said elements to snap said spring member into engagement with the other of said pair of elements; and means for adjusting the upper or lower limit of response of said responsive member.

4. In a humidity responsive device, a humidity responsive member; a pair of elements actuated by said member; a reverse curve shape spring member, retained in saidshapeby engagement with one or the other of said elements, and actuated by one of said elements to snap said spring member into engagement with the other of said pair of elements; means for adjusting the limits of response of said humidity responsive member;

and means for adjusting the upper or lower limit of response of said humidity responsive member.

5. In a humidity responsive device, a humidity responsive member; a pair of elements actuated by said member; a reverse curve shape spring member, retained in said shape by engagement with one or the other of said elements, and actuated by one of said elements to snap said spring member into engagement with the other of said pair of elements; and means for adjusting the:

upper or lower limit of response of said humidity responsive member.

JOHN S. BOKEENO. 

